Apparatus for cutting semiconductor crystal

Abstract

An apparatus for cutting a semiconductor crystal ingot into wafers includes a rotary blade, a first sensor, a second sensor and a computing unit. The blade is of a generally disk shape having a mark put thereon. The first sensor is stationarily located in opposed relation to the blade for sensing a distance between the blade and the first sensor to produce a first signal representative of the distance. The second sensor is stationarily disposed in opposed relation to the blade for detecting the mark of the blade to produce a second signal representative of a position of the mark. The computing unit is connected to the first and second sensors for receiving the first signal from the first sensor in synchronization with the second signal from the second sensor, and computing an amount of warp of the blade as to a fixed position thereof by using the received first signal.

What is claimed is: 
     
       1. An apparatus for cutting a semiconductor crystal, comprising: a rotary blade of a generally disk shape including an inside diameter saw having abrasive grains deposited along an inner periphery thereof;   rotary chuck means fixed holding said blade for rotation therewith;   position indicating means for indicating a position corresponding to a prescribed point on said blade, said position indicating means consisting of a mark on said rotary chuck means;   a first sensor stationarily located in opposed relation to said abrasive grains on said blade for sensing a distance between said blade and said first sensor to produce a first signal representative of said distance;   a second sensor stationarily disposed in opposed relation to said rotary chuck means for detecting said position of said position indicating means to produce a second signal representative of said prescribed point on said blade;   computing means connected to said first and second sensors for receiving said first signal from said first sensor in synchronization with said second signal from said second sensor, and computing an amount of warp of said blade as to a fixed position thereof by using said received first signal, said computing means including a memory for storing as initial data said first signal initially inputted from said first sensor, and processing means for retrieving said stored initial data from said memory and comparing said initial data with said first signal subsequently imputted from said first sensor to thereby calculate said amount of warp of said blade;   command means connected to said computing means for producing a command signal to start the cutting operation, and inputting said command signal to said computing means to cause said computing means to receive said first signal from said first sensor after said command signal is inputted thereto; and   recording means connected to said computing means for recording the amount of warp computed in said computing means.   
     
     
       2. An apparatus according to claim 1, in which said first sensor is comprised of an eddy-current sensor for producing an analog signal serving as said first signal. 
     
     
       3. An apparatus according to claim 1, in which said inside diameter saw includes a recess formed in one of opposite faces thereof and serving as said position indicating means. 
     
     
       4. An apparatus according to claim 1, in which said second sensor is comprised of an eddy-current sensor for producing a series of timing pulses each serving as said second signal. 
     
     
       5. An apparatus according to claim 4, in which said computing means comprises an analog-to-digital converter for receiving said analog signal from said first sensor in synchronization with said timing pulses from said second sensor and translating said received analog signal into a digital signal. 
     
     
       6. An apparatus according to claim 1, wherein comparator means is connected to said first sensor for receiving said first signal from said first sensor and determining whether the position of said first sensor relative to said blade is within a prescribed range to provide information as to the position of said first sensor. 
     
     
       7. An apparatus according to claim 6, wherein display means is connected to said comparator means for displaying said information as to the position of said blade.